Chemical composition studies on some aquatic macrophytes in three Scottish lochs. I. Chlorophyll,ash, carbon,nitrogen and phosphorus.

The chlorophyll, ash, carbon, nitrogen and phosphorus levels in seven species of freshwater macrophytes (Juncus effusus L., Iris pseudacorus L., Carex rostrata Stokes, Glyceria maxima (Hartm.) Holmberg, Nuphar lutea (L) Sm., Polygonum amphibium L. and Schoenoplectus lacustris (L) Pallas) in three Scottish lochs of different trophic levels were studied during 1975. Mean chlorophyll levels varied from a minimum of 1.73 mg g^–1 dry weight in Balgavies Loch Juncus to 10.22 mg g^–1 dry weight for Forfar Loch Iris. Carbon contents ranged from 450 to 520 mg g^–1 ash-free dry weight. For ash, nitrogen and phosphorus, significant differences in mean concentrations were detected among plant species as well as within one plant species growing in different lochs. Positive correlations were apparent between the degree of eutrophication in the study areas and the amount of ash, phosphorus and nitrogen present in the plants growing in them.     

Shoot development and production studies of phragmites Australis (Cav.) Trin. Ex Steudel in Scottish Lochs

Studies were made on the development and production of Phragmites australis (Cav.) Trin. ex Steudel (= Phragmites communis Trin.) stands from Forfar Loch-polytrophic, Balgavies Locheutrophic and Loch of the Lowes-mesotrophic. Differences were detected in the shoot height, shoot dry weight, standing crop biomass, leaf area index, crop growth rate and net efficiency of solar energy conversion among the three lochs. Such differences were partly due to the different nutrient levels of the three locations. The percentage ratio of leaf to shoot weight, leaf area ratio, relative growth rate and net assimilation rate for the reed stands in the three lochs were also calculated and were compared with values from other study areas.     

Rhizome dynamics and resource storage in Phragmites australis

Seasonal changes in rhizome concentrations of total nonstructural carbohydrates (TNC), water soluble carbohydrates (WSC), and mineral nutrients (N, P and K) were monitored in two Phragmites australis stands in southern Sweden. Rhizome biomass, rhizome length per unit ground area, and specific weight (weight/ length ratio) of the rhizomes were monitored in one of the stands.Rhizome biomass decreased during spring, increased during summer and decreased during winter. However, changes in spring and summer were small (< 500 g DW m-2) compared to the mean rhizome biomass (approximately 3000 g DW m^–2). Winter losses were larger, approximately 1000 g DW m-2, and to a substantial extent involved structural biomass, indicating rhizome mortality. Seasonal changes in rhizome length per unit ground area revealed a rhizome mortality of about 30% during the winter period, and also indicated that an intensive period of formation of new rhizomes occurred in June.Rhizome concentrations of TNC and WSC decreased during the spring, when carbohydrates were translocated to support shoot growth. However, rhizome standing stock of TNC remained large (> 1000 g m^–2). Concentrations and standing stocks of mineral nutrients decreased during spring/ early summer and increased during summer/ fall. Only N, however, showed a pattern consistent with a spring depletion caused by translocation to shoots. This pattern indicates sufficient root uptake of P and K to support spring growth, and supports other evidence that N is generally the limiting mineral nutrient for Phragmites.The biomass data, as well as increased rhizome specific weight and TNC concentrations, clearly suggests that reloading of rhizomes with energy reserves starts in June, not towards the end of the growing season as has been suggested previously. This resource allocation strategy of Phragmites has consequences for vegetation management.Our data indicate that carbohydrate reserves are much larger than needed to support spring growth. We propose that large stores are needed to ensure establishment of spring shoots when deep water or stochastic environmental events, such as high rhizome mortality in winter or loss of spring shoots due to late season frost, increase the demand for reserves.     

Tolerance and bioaccumulation of copper in Phragmites australis and Zea mays

The effects of copper on the growth, tolerance indices, mineral composition (N, P, K, Fe, Zn and Mn) and metal uptake of reed (Phragmites australis [Cav. Trin. ex Steudel]) and maize (Zea mays L.) were investigated in hydroponic experiments at copper concentrations ranging from 0.5 to 157 M Cu. A reduction in root length was shown to be a good indicator of copper toxicity, concentrations of 15.7 and 78.7 M Cu inhibiting root growth in maize and reed, respectively. The reed was significantly more tolerant of copper than maize and at 7.85 M Cu (external concentration), reed can be described as a Cu tolerant plant, and maize as a Cu non-tolerant species. As a result of Cu toxicity, the concentrations of macronutrients N, P and K decreased in both shoot and root of maize, while the concentrations were hardly affected in reed tissues. Fe concentration increased in shoots and roots of maize and in roots of reed with increasing Cu treatments, leading to highly significant (p<0.01) linear relationships between tissue Fe and Cu concentrations. The bioconcentration factor (BCF) of Cu was higher in roots than in shoots of both plant species, ranging from 612 to 1592 in reed for the Cu treatments tested. In the roots of maize, BCF of Cu increased from 349 to 1931 when increasing Cu in nutrient solution from 7.85 M to 78.5 M. Therefore, reed could be useful in wastewater treatments for the removal of Cu. However, the use of reed in phytoextraction of Cu from contaminated soils is limited by the low accumulation rate in shoots and although reed can be more efficient than maize for Cu phytoextraction, harvesting the full biomass, including roots, may be required.     

Zinc distribution and zinc-binding forms in Phragmites australis under zinc pollution

The influence of zinc (Zn) on physiological and biochemical parameters was studied to elucidate the mechanism of Zn resistance in Phragmites australis. Zn concentrations in roots, stems and leaves increased with exogenous Zn concentration, while Zn content in roots was much higher than in shoots. X-ray microanalysis was used to reveal compartments in which Zn accumulated in root cortex. Zinc concentrations followed a gradient with the sequence: intercellular space>cell wall >vacuole >cytoplasm, indicating that most Zn was immobilized in the apoplast or sequestered into the vacuolar lumen. Sequential extraction of various Zn chelates revealed that the ratio of Zn extracted with different extraction media was markedly different. Ethanol, HAc (acetic acid) and NaCl-extractable Zn were dominant in both roots and leaves of P. australis. Zn-binding protein fractions were found in the roots and leaves after gel filtration chromatography, among which a polypeptide with an apparent molecular mass of 14kDa bound Zn most effectively. Two newly synthesized polypeptides of 58 and 45kDa appeared under Zn pollution, whereas a prominent fraction of 72kDa disappeared. The involvement of Zn distribution in plant tissues, subcellular compartments and chelates and Zn-inducing proteins in the acclimation mechanism of P. australis to Zn pollution is discussed.     

Tissue culture and long-term regeneration of Phragmites australis (Cav.) Trin. ex Steud.

Phragmites australis tissue cultures were initiated from mature seeds on MS medium supplemented with 1 mgl^-1 each of 2,4-D and IAA. Cultures displayed typical embryogenic callus that was compact and bright yellow. Selection for embryogenic callus established long-term regenerable cultures. Removal of auxin from the basal medium allowed numerous complete plants to be recovered from the cultures. Histological study indicated both the presence of embryogenic-type cells and the bipolar development of regenerated plants.     

Effects of an organic sediment on performance of young Phragmites australis clones at different water depth treatments

Performance of young Phragmites australis plants was examined after 7 weeks on an artificial nutrient-enriched inorganic substrate and on the same substrate to which an organic sediment from a eutrophic lake was added, at three different water depth treatments. Growth decreased, and proportional allocation of biomass to roots increased, with the addition of sediment. These differences were significant in shallow and deep water, but not at a medium depth. Concentrations of phosphorus and nitrogen in plant biomass decreased, and concentration of iron increased, with addition of sediment.The effects of sediment addition may have resulted from a decreased availability of nutrients in the substrate or from an impaired root functioning. Nutrient exhaustion in the substrate, due to a fast plant growth, can explain the relatively strong effects in shallow water. Deep water, on the other hand, probably restricted oxygen transport to the roots, resulting in an impaired root functioning in the low-redox sediment environment. The results show that, especially in relatively deep water, growth of undisturbed plants of P. australis may be inhibited by eutrophication of sediments, probably because of an impaired root functioning in sediments containing reduced toxic compounds (e.g. ferrous iron).     

Ramet size equalisation in a clonal plant,Phragmites australis

The influence of shading from older generations of dead culms (standing litter) on density, growth rate and development of size structure at the ramet level was investigated in a pure stand of Phragmites australis by experimental neutral shading of plots after removal of standing litter. Initial differences in height distribution between autumn and spring cohorts disappeared in the course of shoot growth. The Gini coefficients of shoot heights and estimated shoot weights indicated that the size structure of the shoots became more equal with increasing mean size in both shaded and unshaded plots. Relative growth rate for height (RHGR) and weight of individual shoots was negatively related to shoot size during the early and presumably storage-dependent growth period, suggesting a strong support for growth of smaller shoots. No etiolation was indicated by mean or maximum height in shaded and unshaded plots, or by the relationship between shoot height and weight. Mean shoot density was significantly lower in shaded than in unshaded plots in one of two shade treatment years. A regression model indicated a small but significant effect of shoot density on the approximately linear relationship between RHGR and the logarithm of height. The growth rate of small shoots was slightly larger at low than at high shoot density. Therefore, it is suggested that the shade from standing litter in P. australis stands can decrease shoot natality in the spring cohort, and thereby increase the support to fewer small shoots.     

Plant regeneration from embryogenic cultures of Phragmites australis (Cav.) Trin. Ex Steud.

Embryogenic cultures of the common reed [Phragmites australis (Cav.) Trin. Ex. Steud.] were induced on Murashige and Skoog (1962)-based medium with 2% (w/v) sucrose, B5 vitamins and 4.5 μM 2,4-dichlorphenoxyacetic acid. Four independent culture lines, two initiated from stem nodes and two from roots, were established. These cultures underwent somatic embryogenesis. In one line of stem node origin, the somatic embryos germinated and developed into plants, following transfer of embryogenic cultures to Murashige and Skoog (1962)-based medium lacking growth regulators, with 108 ± 17 plants being recovered per 100 mg fresh weight of culture. In other lines, the somatic embryos developed roots, but not shoots. Shoot regeneration via somatic embryogenesis offers potential as anin vitro system for physiological studies, including assessments of the response of common reed to environmental pollutants. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effects of salinity and cutting on the development of Phragmites australis

The effects of increased salinity and cutting the above ground biomass on the growth of Phragmites australis were evaluated by investigating four experimental reed stands grown in outdoor tanks. Two stands were treated with 30 salinity and the other two stands with freshwater; one stand of each treatment was cut to 20 cm during the second growing season. Growth conditions were observed until all the plants were dead at the end of the second year. The number of shoots emerged from the freshwater-treated stand was about 70% higher than that of the saltwater-treated stand. The number of shoots emerged from cut plant stands were markedly lower than uncut stands. The average shoot height was negatively affected by salinity and shoots that emerged after cutting further decreased in height. The average number of leaves on a shoot was not significantly affected by salinity, but reduced by cutting in both treatments. Leaf length, width and the distance between leaves were decreased by both salinity and cutting. In the freshwater-treated uncut stand more than 50% of the shoots formed panicles, but this proportion was reduced to 6% by salinity, to 15% by cutting, and to 0% by the combination of salinity and cutting. This study showed again that salinity reduces the growth of aboveground components. The growth, however, was most severely retarded by cutting combined with salinity, which has many implications for better management of P. australis stands.     

Effects of rhizome age on the decomposition rate of Phragmites australis rhizomes

The change in dried rhizome samples that were left to decompose was investigated to elucidate the effects of rhizome age on the decomposition rate of Phragmites australis. Rhizomes were classified into five age categories and placed 30 cm below the soil surface of a reed stand. After 369 days of decay, new (i.e., aged less than one year) rhizomes had lost 84% of their original dry mass, compared with a loss of 41–62% for that of older rhizomes. The exponential decay rates of older rhizomes were nearly identical to that of aboveground biomass. The nitrogen (N) concentration increased to two times its original values, but the phosphorus (P) concentration remained constant after an initial loss by leaching. The carbon to nitrogen (C:N) and carbon to phosphorus ratios (C:P) leveled out at 22:1 to 38:1 and 828:1 to 1431:1, respectively, regardless of rhizome age. The results are important to understand the nutrient cycles of reed-dominant marsh ecosystems.     

Human Facilitation of Phragmites australis Invasions in Tidal Marshes: A Review and Synthesis

Efforts to manage or prevent Phragmites australis invasion in salt and brackish marshes are complicated by the lack of a general causal role for specific human activities. The pattern of invasion within a marsh differs among sites, and each may have different causal histories. A review of the literature finds three establishment/invasion patterns: (1) from stands established on ditch- or creek-bank levees toward interior portions of high marshes, (2) from stands along upland borders toward high marsh interiors, and (3) centroid spread from high marsh stands established in ostensibly random locations. Each invasion pattern seems to have different anthropogenic precursors, therefore preventing generalizations about the role of any one human activity in all sites. However, historical and experimental evidence suggests that regardless of invasion pattern, establishment is much more likely at sites where rhizomes are buried in well-drained, low salinity marsh areas. Any human activity that buries large rhizomes, increases drainage, or lowers salinity increases chances of establishing invasive clones. To integrate these patterns and improve our understanding of the rapid spread of Phragmites, recent evidence has been synthesized into a dichotomous flow chart which poses questions about current site conditions and the potential for proposed activities to change site conditions that may facilitate invasion. This simple framework could help managers assess susceptibility and take preventative measures in coastal marshes before invasion occurs or before removal becomes very expensive.     

Effect of broken dead culms of Phragmites australis on radial oxygen loss in relation to radiation and temperature

The amount of oxygen released from the roots of Phragmites australis was quantified to examine the effects of airflow through dead culms, radiation, and temperature on radial oxygen loss (ROL). To investigate the effect of dead culms on ROL quantitatively, the ROL of individual plants with open dead culms was compared to that of plants with sealed dead culms as a function of light intensity and temperature. The relationship between ROL and plant morphology (aboveground biomass, shoot diameter, shoot height) was investigated. When exposed to 300, 600, and 900 μmol m⁻² s⁻¹ light, the ROL was 15.6, 22.5, and 30.9 μmol O₂ g⁻¹ dry root day⁻¹, respectively, from plants with open dead culms and 11.0, 16.4, and 23.3 μmol O₂ g⁻¹ dry root day⁻¹, respectively, from plants with sealed dead culms. The ROL from plants with open dead culms was obviously higher than that from plants with sealed dead culms in every condition. The ROL from plants with open culms was 37% and 30% higher than that from plants with sealed culms at 20°C and 30°C, respectively. The effects of plant-specific parameters such as leaf area and shoot diameter on radial oxygen loss were evident. From the point of view of rhizosphere oxidation during the growing season, the existence of open dead culms should be taken into consideration for optimal plant management in constructed wetlands. This study provides a theoretical understanding of the effects of open dead culms, light conditions, and temperature on radial oxygen loss. Handling editor: S. M. Thomaz     

Increasing the efficiency of reed plantations on stressed lake and river shores by using special clones of Phragmites australis

In an investigation aimed at comparing the variationin growth and expansion of different reed clones, 10reed clones were planted in spring of 1995 on sixexperimental fields on the River Dahme and the RiverHavel in Berlin. Their sites of origin differed innutrient supply, substrate quality and shoreexposition. The main aim of this large-scaleexperiment was to search for reed clones that would beable to colonize lake shores rapidly and to expandinto deeper water. Two years after planting thedeveloping reed stands differed significantly inmorphology and stand structure, both among clones andamong sites. This indicates that the development ofreed stands depended on the environment as well as onthe genotype. The differences in development impliedthat some of the clones would be more suited thanothers for restoration purposes, so that successfulrestoration of a degraded river or lake shores mightdepend on the selection of the best suited clones.The nitrogen contents in the aboveground biomass oftwo clones differing in nitrogen dynamics at theiroriginal sites (described as `assimilation' and`translocation' types in the literature) did notdiffer in this experiment, even though the two clonesdid differ in some morphological traits. These resultsmight be influenced by the fact that stands were stilldeveloping and that possibly clones had reached adifferent degree of maturity. Nevertheless, theysuggest that nitrogen content depends more on siteconditions, with only little genetically determineddifference, and that morphological variation isdetermined by factors other than variation in nitrogenuptake.     

Growth,chlorophyll and mineral nutrient studies on phalaris arundinaceae L. in three scottish lochs

Growth, chlorophyll and mineral nutrients studies were made in Phalaris arundinaceae L. in three Scottish lochs of varying nutrient status from March to November in 1975. The maximum shoot height and shoot dry weight attained by the plants were approximately 160 cm and 4 g respectively. Seasonal changes in the chlorophyll levels in the Phalaris leaf were studied and two peaks were found, one in April and the other in June–July. Maximum chlorophyll level attained was 9 mg g^–1 leaf dry weight. The changes in the mineral levels in the root, stem, leaf and inflorescence parts of the plants from the three lochs were also assayed throughout the growing season. A total of eight mineral elements were studied, including carbon, nitrogen, phosphorus, potassium, sodium, calcium, magnesium and iron. Variations in both the mineral concentrations and their pattern of changes during the study period among the plants from the lochs were observed and discussed.     

Blocking Phragmites australis reinvasion of restored marshes using plants selected from wild populations and tissue culture

This study tested a vegetation strategy for controlling Phragmites australis invasion into brackish marshes as an alternative to the current technique of repeated herbicide sprays followed by burning. This strategy involves blocking P. australis by planting desired plants selected from wild populations and/or tissue culture regenerants at key points on the major routes of P. australis invasion. The planting of native species was conducted at three sites in a herbicide-treated P. australis marsh near Salem, NJ. Wild population selections of three upland marsh shrubs, Myrica cerifera, Baccharis halimifolia, and Iva frutescens, as well as two grass species, Spartina alterniflora and Spartina patens, and two rushes, Juncus gerardi and Juncus roemerianus, were planted according to their normal zonation positions. Tissue culture regenerated plants of the two grasses and two rushes, and the sedge species Scirpus robustus, were also planted. Plant growth at each site was monitored each year after planting for up to 3 years. Most plants of B. halimifolia, I. frutescens, J. roemerianus, and S. patens demonstrated a consistent vigorous growth at all three sites, whether or not the plants were collected from wild populations or were tissue culture regenerants. These multi-layered walls of plants demonstrated effectiveness in controlling the P. australis by restricting or inhibiting its spread. Upon screening 48 regenerated plants of S. patens at one of the three sites, we found that some regenerants showed enhanced characteristics for blocking P. australis, such as greater expansion and a high stem density. The availability of the tissue culture-regenerated plants of the native marsh species makes it possible to select lines from local genotypes that have desirable characteristics for wetland restoration projects, such as blocking P. australis reinvasion.     

Variability of the grass Phragmites australis in relation to the behaviour and mortality of the gall-inducing midge Giraudiella inclusa (Diptera,Cecidomyiidae)

Summary Variability within and between shoots of the grass Phragmites australis proved to be important for both survival (successful gall induction) and reproduction (larval weight) of the gall-inducing midge Giraudiella inclusa. The ovipositing females and the migrating first instar larvae chose a predictable microhabitat within shoots and within internodes characterized by a high nutritional quality (nitrogen, mineral content, sugar, water) and reduced palnt defense properties (silicate). Clutch size increased with the shoot diameter, larval scramble competition could not be detected. Female shoot selection was random, although the chances of successful gall induction greatly differed between shoots. Thick and intact shoots (6 mm) led to a high larval mortality. But thick shoots destroyed apically by stem-mining caterpillars (of the noctuid moth Archanara geminipuncta) had on average large gall clusters. Accordingly, the adjustment of the clutch size to the shoot diameter resulted in an advantage for the gall midge females only when shoots were thin and short (i.e. stressed by water and nutrient deficiency) or heavily damage (i.e. stressed) by caterpillars. Thus, the monophagous gall maker G. inclusa did not compensate for all features of intershoot variation of P. australis, although grasses are well-known for their simple plant architecture and their low diversity and low concentration of secondary compounds.     

Changes in the fauna of the stony substratum of lakes in the english lake district

Development of foliage structure in Phragmites australis (Cav.) Trin. ex Steudel stands in three Scottish lochs in 1975 was studied. Both tagged and harvested shoots were utilized to monitor the seasonal changes in the chlorophyll content, net leaf number, rate of shoot elongation, leaf production, leaf fall and leaf area increase, and individual leaf size in the reed-stands from the three study areas. Quantitative measurements of the number of leaf and leaf surface area in 25 cm stratified layers in the shoots were also made during active canopy development from May to August.     

Management of Phragmites australis in Swiss fen meadows by mowing in early summer

Mowing experiments were carried out from1995 to 2001 in Swiss fen meadows toinvestigate whether the abundance of Phragmites australis is reduced by mowingin early summer in addition to mowing inautumn. Experimental plots of 100 m²were established in three fen meadows thatare mown every year in September; treatedplots received an additional cut in lateJune either every year or every two years.Until 1997, the additional cut had noeffect on the above-ground biomass of Phragmites (monitored every year in lateJune). As from 1998, the biomass of Phragmites was 25–30% lower in the plotswith annual June cut than in the controlplots. However, the pooled biomass of allother plant species decreased similarly, sothat the degree of dominance of Phragmites was not reduced. An additionalJune cut every two years had no effect onthe biomass of Phragmites. In June2001, the shoots of Phragmites weresmaller in annually June-cut plots than incontrol plots, but allometric relationshipsbetween shoot length and diameter, shootgrowth from June to August, and nitrogenand phosphorus concentrations of shoots didnot differ between June-cut and controlplots. The additional June cut increasedthe total export of N with the hay by 18%,and that of P by 50% in 2001. Theseadditional nutrient exports were smallerthan those found in the first years of theexperiment and not larger for Phragmites than for the remainder of thevegetation. Together, the results suggestthat a depletion of below-ground storescaused Phragmites to decrease afterseveral years of additional mowing in June.Eighty further permanent quadrats in fenmeadows with normal management (mownannually in September) were surveyed in1995–96 and in 2001. The above-groundbiomass of Phragmites increasedduring this time in 49 out of 80 plots,with a mean relative difference of +35.5%.Thus, even if additional mowing in earlysummer only slightly reduced theperformance of Phragmites compared toplots mown only in September, thistreatment might help to prevent the speciesfrom spreading under the current conditionsin Swiss fen meadows.     

Occurrence of Puccinia isiacae on Phragmites australis in Saudi Arabia and its possibility as a biological control agent

During the summer of 2002, symptoms of rust disease were observed for the first time on Phragmites australis in Saudi Arabia. Light brown lesions of regular shape indicating uredinia of Puccinia isiacae appeared on the leaves. The morphology and characteristics of the fungus were described in detail with both light and scanning electron microscopy. The possibility of using this fungus as a biological control agent was also discussed.